Optical system and imaging apparatus including the same

ABSTRACT

In an optical system according to each exemplary embodiment, an interval between adjacent lens units changes in focusing from an infinite-distance object to a close-distance object, and a first in-focus state in which β=−1.2 is obtained can be caused, where β is a lateral magnification of an entire system. The optical system according to each exemplary embodiment includes a plurality of focus lens units, and out of a focus lens unit having a largest absolute value of a focus sensitivity and a focus lens unit having a second largest absolute value of a focus sensitivity in a state in which focus is put on an infinite-distance object, a focus lens unit disposed on an object side is a lens unit LA, and a focus lens unit disposed on an image side is a lens unit LB. A partial optical system LC including all lenses disposed on the image side of the lens unit LB has negative refractive power. The partial optical system LC satisfies a predetermined conditional expression.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. Application No. 16/592391,filed Oct. 3, 2019, which claims priority from Japanese PatentApplication No. 2018-194671, filed Oct. 15, 2018, which are herebyincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an optical system, which is suitablefor digital video cameras, digital still cameras, broadcasting cameras,silver-halide film cameras, monitoring cameras, and the like.

Description of the Related Art

A macro lens is known as a lens that can perform close-up imagecapturing. In recent years, there has been demand for a macro lens thatcan capture an image of an infinite-distance object, and can alsoperform close-up image capturing at an imaging magnification increasedto the same magnification or more.

Japanese Patent Application Laid-Open No. 2015-034899 discusses anoptical system (a macro lens) that can perform enlarged image capturing,enlarged from an infinite-distance object to about a 2× imagingmagnification.

By positioning a lens unit with positive refractive power at the closestposition to an image plane (IP) on an image side, the optical systemdiscussed in Japanese Patent Application Laid-Open No. 2015-034899shortens the moving distance of a focus lens unit, during focusing, andsuppresses a decline in optical performance for enlarged imagecapturing. However, a lens diameter may be increased as imagingmagnification increases.

SUMMARY OF THE INVENTION

The present invention is directed to a compact optical system that hashigh optical performance and can perform image capturing at an imagingmagnification of a same magnification or more, and an imaging apparatusincluding the optical system.

According to an aspect of the present invention, An optical system inwhich an interval between adjacent lens units is configured to changeduring focusing from an infinite-distance object to a close-distanceobject, and in which in a first in-focus position β=-1.2 is satisfied,where β is a lateral magnification of the optical system, includes aplurality of focus lens units configured to move during focusing from aninfinite-distance object to a close-distance object, wherein, out of afocus lens unit having a largest absolute value of a focus sensitivityand a focus lens unit having a second largest absolute value of a focussensitivity among the plurality of focus lens units in an in-focus stateon an infinite-distance object, a focus lens unit disposed on an objectside is a first focus lens unit (LA), and a focus lens unit disposed onan image side is a second focus lens unit (LB), wherein a partialoptical system (LC) including all lenses disposed on the image side ofthe second focus lens unit (LB) has negative refractive power, andwherein the following conditional expression is satisfied:

−3.00<fLCX/fX<−0.50,

where fLCX is a focal length of the partial optical system (LC) in thefirst in-focus state, and fX is a focal length of the optical system inthe first in-focus state.

According to another aspect of the present invention, an imagingapparatus includes an optical system, and an image sensor configured tophotoelectrically convert an optical image formed by the optical system,wherein, in the optical system, an interval between adjacent lens unitschanges in focusing from an infinite-distance object to a close-distanceobject, and a first in-focus state in which β=−1.2 is satisfied can beachieved, where β is a lateral magnification of an entire system,wherein the optical system includes a plurality of focus lens unitsconfigured to move in focusing from an infinite-distance object to aclose-distance object, wherein, out of a focus lens unit having alargest absolute value of a focus sensitivity and a focus lens unithaving a second largest absolute value of a focus sensitivity among theplurality of focus lens units in an in-focus state on aninfinite-distance object, a focus lens unit disposed on an object sideis a lens unit LA, and a focus lens unit disposed on an image side is alens unit LB, wherein a partial optical system LC including all lensesdisposed on the image side of the lens unit LB has negative refractivepower, and wherein the following conditional expression is satisfied:

−3.00<fLCX/fX<−0.50,

where fLCX is a focal length of the partial optical system LC in thefirst in-focus state, and fX is a focal length of the optical system inthe first in-focus state.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional diagrams of an optical systemaccording to a first exemplary embodiment.

FIGS. 2A, 2B, 2C, and 2D are aberration diagrams of the optical systemaccording to the first exemplary embodiment.

FIGS. 3A and 3B are cross-sectional diagrams of an optical systemaccording to a second exemplary embodiment.

FIGS. 4A, 4B, 4C, and 4D are aberration diagrams of the optical systemaccording to the second exemplary embodiment.

FIGS. 5A and 5B are cross-sectional diagrams of an optical systemaccording to a third exemplary embodiment.

FIGS. 6A, 6B, 6C, and 6D are aberration diagrams of the optical systemaccording to the third exemplary embodiment.

FIGS. 7A and 7B are cross-sectional diagrams of an optical systemaccording to a fourth exemplary embodiment.

FIGS. 8A, 8B, 8C, and 8D are aberration diagrams of the optical systemaccording to the fourth exemplary embodiment.

FIGS. 9A and 9B are cross-sectional diagrams of an optical systemaccording to a fifth exemplary embodiment.

FIGS. 10A, 10B, 10C, and 10D are aberration diagrams of the opticalsystem according to the fifth exemplary embodiment.

FIGS. 11A and 11B are cross-sectional diagrams of an optical systemaccording to a sixth exemplary embodiment.

FIGS. 12A, 12B, 12C, and 12D are aberration diagrams of the opticalsystem according to the sixth exemplary embodiment.

FIGS. 13A and 13B are cross-sectional diagrams of an optical systemaccording to a seventh exemplary embodiment.

FIGS. 14A, 14B, 14C, and 14D are aberration diagrams of the opticalsystem according to the seventh exemplary embodiment.

FIGS. 15A and 15B are cross-sectional diagrams of an optical systemaccording to an eighth exemplary embodiment.

FIGS. 16A, 16B, 16C, and 16D are aberration diagrams of the opticalsystem according to the eighth exemplary embodiment.

FIG. 17 is a schematic diagram of an imaging apparatus.

DESCRIPTION OF THE EMBODIMENTS

An optical system according to an exemplary embodiment of the presentinvention, and an imaging apparatus including the optical system will bedescribed based on the attached drawings. Each of the embodiments of thepresent invention described below can be implemented solely or as acombination of a plurality of the embodiments. Also, features fromdifferent embodiments can be combined where necessary or where thecombination of elements or features from individual embodiments in asingle embodiment is beneficial.

FIGS. 1A, 3A, 5A, 7A, 9A, 11A, 13A, and 15A are cross-sectional diagramsof optical systems according to first to eighth exemplary embodiments,each illustrating an in-focus state on an infinite-distance object.FIGS. 1B, 3B, 5B, 7B, 9B, 11B, 13B, and 15B are cross-sectional diagramsof the optical systems according to the first to eighth exemplaryembodiments, each illustrating aa in-focus state on a finite-distanceobject. An imaging magnification set in this state is illustrated ineach diagram. The optical system according to each of the exemplaryembodiments is an optical system used in an imaging apparatus such asdigital video cameras, digital still cameras, broadcasting cameras,silver-halide film cameras, or monitoring cameras.

In each of the lens cross-sectional diagrams, the left side correspondsto an object side and the right side corresponds to an image side. Theoptical system according to each of the exemplary embodiments includes aplurality of lens units. In this disclosure, a lens unit refers to agroup of lenses integrally moving or stopping in focusing. In otherwords, in the optical system according to each of the exemplaryembodiments, an interval between adjacent lens units changes in focusingfrom an infinite-distance object to a close-distance object. Inaddition, a lens unit may only include a single lens or may include aplurality of lenses. In addition, a lens unit may include an aperturestop.

In each of the lens cross-sectional diagrams, “Li” denotes an i-th lensunit disposed at an i-th (“i” is a natural number) position when beingcounted from the object side. In addition, “SP” denotes a main stop(aperture stop) for determining (limiting) an F-number (Fno) light beam,and “SP2” denotes a sub stop for reducing a stop diameter in accordancewith a change in imaging magnification and cutting unnecessary lightrays. “IP” denotes an image plane. When the optical system according toeach of the exemplary embodiments is used as an imaging optical systemof a digital still camera or a digital video camera, an imaging plane ofa solid-state image sensor (photoelectric conversion device) such as acharge-coupled device (CCD) sensor or a complementary metal-oxidesemiconductor (CMOS) sensor is disposed at the image plane IP. When theoptical system according to each of the exemplary embodiments is used asan imaging optical system of a silver-halide film camera, aphotosensitive surface corresponding to a film surface is placed at theimage plane IP. “GB” denotes an optical filter placed on the object sideof the image plane IP.

In addition, the optical system according to each of the exemplaryembodiments includes a plurality of focus lens units. A focus lens unitrefers to a lens unit moving in focusing. Arrows illustrated in each ofthe lens cross-sectional diagrams indicate moving directions of thefocus lens units in focusing from an infinite-distance object to aclose-distance object.

FIGS. 2A, 2B, 2C, 2D, 4A, 4B, 4C, 4D, 6A, 6B, 6C, 6D, 8A, 8B, 8C, 8D,10A, 10B, 10C, 10D, 12A, 12B, 12C, 12D, 14A, 14B, 14C, 14D, 16A, 16B,16C, and 16D are aberration diagrams of the optical systems according tothe first to eighth exemplary embodiments. In the aberration diagrams,aberration diagrams illustrated in FIGS. 2A, 4A, 6A, 8A, 10A, 12A, 14A,and 16A are aberration diagrams illustrating an in-focus state on aninfinite-distance object, and aberration diagrams illustrated in FIGS.2B to 2D, 4B to 4D, 6B to 6D, 8B to 8D, 10B to 10D, 12B to 12D, 14B to14D, and 16B to 16D are aberration diagrams illustrating an in-focusstate on a finite-distance object. Lateral magnifications in theaberration diagrams illustrated in FIGS. 2B to 2D, 4B to 4D, 6B to 6D,8B to 8D, 10B to 10D, 12B to 12D, 14B to 14D, and 16B to 16D are asillustrated in the corresponding aberration diagrams.

In each spherical aberration diagram, “Fno” denotes an F-number, andspherical aberration amounts with respect to d-line (wavelength of 587.6nm) and g-line (wavelength of 435.8 nm) are illustrated. In eachastigmatism diagram, “AS” denotes an astigmatism amount on a sagittalimage plane, and “ΔM” denotes an astigmatism amount on a meridionalimage plane. In each distortion aberration diagram, a distortionaberration amount with respect to d-line is illustrated. In eachchromatic aberration diagram, a chromatic aberration amount in g-line isillustrated. In aberration diagrams, “ω” denotes an imaging half fieldangle (°).

Next, a characteristic configuration of the optical system according toeach of the exemplary embodiments will be described.

The optical system according to each of the exemplary embodiments is amacro lens that can perform image capturing at least in an in-focusstate in which β=−1.2 is obtained. Hereinafter, the in-focus state inwhich β=−1.2 is obtained will be referred to as a first in-focus state.

If a total lens length of a macro lens is to be shortened, it sometimesbecomes difficult to achieve both the correction of spherical aberrationor comatic aberration, and the correction of field curvature especiallyin an in-focus state on a close-distance object. For this reason, in theoptical system according to each of the exemplary embodiments, aso-called floating system is employed by providing a plurality of focuslens units. Hereinafter, in the optical system according to each of theexemplary embodiments, out of a lens unit having the largest absolutevalue of a focus sensitivity and a lens unit having the second largestabsolute value of a focus sensitivity among a plurality of focus lensunits in an in-focus state on an infinite-distance object, a lens unitdisposed on the object side will be referred to as a first focus lensunit LA, and a lens unit disposed on the image side will be referred toas a second focus lens unit LB. The first and second focus lens units LAand LB can be said to be lens units having a main focusing function inthe optical system according to each of the exemplary embodiments. Inaddition, a focus sensitivity ESi of an arbitrary lens unit Li isdefined by the following expression:

ESi=(1−βi ²)×βr ²,

-   -   where a lateral magnification of the lens unit Li in an in-focus        state on an infinite-distance object is denoted by βi, and a        combined lateral magnification of all lens units disposed on the        image side of the lens unit Li is denoted by βr.

When the floating system is employed, if an imaging magnification is tobe increased to such a degree that image capturing can be performed inthe first in-focus state, an amount of movement of each focus lens unitbecomes large. For this reason, it becomes necessary to secure an amountof movement of each focus lens unit, and it becomes difficult to shortena total lens length.

Thus, in the optical system according to each of the exemplaryembodiments, refractive power of a partial optical system LC includingall the lenses disposed on the image side of the second focus lens unitLB is appropriately set. The optical system according to each of theexemplary embodiments can thereby have high optical performance whilebeing compact, and can further perform image capturing at high imagingmagnification i.e., a same magnification or more.

Specifically, in the optical system according to each of the exemplaryembodiments, the partial optical system LC has negative refractivepower. With this configuration, because it is possible to dispose anexit pupil at a position close to the image plane, it is possible toshorten a back focus. This enables the total lens length to beshortened. In addition, by setting negative refractive power asrefractive power of the partial optical system LC, it is possible toreduce a lens diameter of a lens disposed at a position close to theimage plane in the optical system.

In addition, the optical system according to each of the exemplaryembodiments satisfies the following Conditional Expression (1):

−3.00<fLCX/fX<−0.50   (1),

where fLCX is a focal length of the partial optical system LC in thefirst in-focus state, and fX is a focal length of the entire opticalsystem in the first in-focus state.

Conditional Expression (1) defines a relationship between a focal lengthof the entire system and a focal length of the partial optical system LCin the first in-focus state. By satisfying Conditional Expression (1),it is possible to achieve both the correction of distortion aberrationor magnification chromatic aberration and the shortening of the totallens length.

If a value of fLCX/fX exceeds an upper limit of Conditional Expression(1), a back focus becomes too short. In this case, it is advantageousfor the shortening of the total lens length, but it becomes difficult tocorrect distortion aberration and/or magnification chromatic aberration.It is possible to correct aberration by increasing the number of lensesof the partial optical system LC, but in this case, the total lenslength is consequently increased.

If negative refractive power of the focal length fCLX becomes smaller orthe focal length fX becomes smaller to such a degree that a value offLCX/fX falls below a lower limit of Conditional Expression (1), itbecomes difficult to secure a working distance in enlarged imagecapturing. In addition, it is advantageous for the correction ofspherical aberration and/or comatic aberration, but a back focus becomeslarger and the total lens length is increased.

In addition, it is more desirable to set a numerical value range ofConditional Expression (1) to a range of the following ConditionalExpression (1a), and it is further desirable to set the numerical valuerange to a range of Conditional Expression (1b).

−2.70<fLCX/fX<−0.60   (1a)

−2.30<fLCX/fX <−0.63   (1b)

With the configuration described above, the optical system according toeach of the exemplary embodiments can perform image capturing at animaging magnification of a same magnification or more, and can becompact while having high optical performance.

Next, conditions to be desirably satisfied by the optical systemaccording to each of the exemplary embodiments will be described. Theoptical system according to each of the exemplary embodiments desirablysatisfies one or more conditional expressions of the followingConditional Expressions (2) to (11). In Conditional Expression (2), fLCYis a focal length of the partial optical system LC in a second in-focusstate in which β=−1.0 is obtained, and f is a focal length of the entireoptical system in a state in which focus is put on an infinite-distanceobject. In Conditional Expression (3), fLA is a focal length of thefirst focus lens unit LA. In Conditional Expression (4), sk is adistance from an image-side lens surface of a lens disposed closest tothe image side in the optical system, to the image plane that is set ina state in which focus is put on an infinite-distance object (a backfocus in air conversion). In Conditional Expression (5), ESA is a focussensitivity of the first focus lens unit LA in a state in which focus isput on an infinite-distance object. In Conditional Expression (6), ESBis a focus sensitivity of the second focus lens unit LB in a state inwhich focus is put on an infinite-distance object. In ConditionalExpression (7), MA is an amount of movement of the first focus lens unitLA moved from a state in which focus is put on an infinite-distanceobject, until the second in-focus state ((β=−1.0) is caused, and MB isan amount of movement of the second focus lens unit LB moved from astate in which focus is put on an infinite-distance object, until thesecond in-focus state is caused. In Conditional Expression (8), Di is adistance from the aperture stop SP to the image plane IP in a state inwhich focus is put on an infinite-distance object. In ConditionalExpression (9), fL1 is a focal length of a first lens unit L1 in a statein which focus is put on an infinite-distance object. In ConditionalExpression (10), fI is a focal length of a lens disposed closest to theimage side in the optical system. In addition, a lens disposed closestto the image side is a single lens element in the optical systemaccording to each of the exemplary embodiments, but a lens disposedclosest to the image side may be a cemented lens. In this case, fI is afocal length in air of a lens disposed closest to the image side amongthe cemented lens disposed closest to the image side (a focal lengthobtainable when the cemented lens is separated and each of the separatedlenses is regarded as a single lens element). In Conditional Expression(11), βm is a lateral magnification obtainable when an imagingmagnification is largest in the optical system according to each of theexemplary embodiments.

−1.20<fLCY/f<−0.20   (2)

0.10<|fLAK|<0.50   (3)

−1.00<sk/fLCY<−0.10   (4)

2.50<|ESA|<7.50   (5)

0.10<|ESB|<6.00   (6)

0.05<(|MA|+|MB|)/f<0.60   (7)

0.50<Di/f<1.50   (8)

0.10<fL1/f<2.50   (9)

0.25<fI/f<2.20   (10)

−5.0<βm<−1.2   (11)

Conditional Expression (2) defines a relationship between the focallength fLCY of the partial optical system LC and a focal length of theentire system in the second in-focus state. By satisfying ConditionalExpression (2), it is possible to achieve both an increase in imagingmagnification and further shortening of the total lens length.

If a value of fLCY/f exceeds an upper limit of Conditional Expression(2), it is advantageous for the shortening of the total lens length, butit becomes easier to generate distortion aberration and/or magnificationchromatic aberration, which is undesirable.

If a value of fLCY/f falls below a lower limit of Conditional Expression(2), it becomes difficult to shorten a back focus and the total lenslength is increased. Thus, it becomes difficult to sufficiently shortenthe total lens length.

Conditional Expression (3) defines a relationship between a focal lengthof the first focus lens unit LA and a focal length of the entire system.By satisfying Conditional Expression (3), it is possible to reduce anamount of movement in focusing while maintaining optical performance,and to further shorten the total lens length.

If a value of |fLA/f| exceeds an upper limit of Conditional Expression(3), refractive power of the first focus lens unit LA decreases and anamount of movement in focusing consequently increases. As a result, itbecomes difficult to sufficiently shorten the total lens length.

If a value of |fLA/f| falls below a lower limit of ConditionalExpression (3), refractive power of the first focus lens unit LAincreases and an amount of change in spherical aberration and/or fieldcurvature in focusing consequently increases.

Conditional Expression (4) defines a relationship between a back focusof the optical system and a focal length of the partial optical systemLC in the second in-focus state. By satisfying Conditional Expression(4), it is possible to further reduce a lens diameter of the partialoptical system LC.

If a value of sk/fLCY exceeds an upper limit of Conditional Expression(4), a back focus becomes too short. In this case, it becomes difficultto dispose a shutter member or the like, and it becomes difficult to usethe optical system according to each of the exemplary embodiments as animaging optical system of an imaging apparatus such as a digital stillcamera.

If a value of sk/fLCY falls below a lower limit of ConditionalExpression (4), a back focus becomes too long and a lens diameterincreases. As a result, it becomes difficult to obtain asufficiently-compact optical system.

Conditional Expression (5) defines the focus sensitivity ESA of thefirst focus lens unit LA.

If a value of |ESA| exceeds an upper limit of Conditional Expression(5), a change in field angle caused by focusing becomes large, which isundesirable. In addition, an amount of change in spherical aberrationand/or field curvature in focusing may become large.

If a value of |ESA| falls below a lower limit of Conditional Expression(5), an amount of movement of the first focus lens unit LA in focusingincreases. As a result, it becomes difficult to sufficiently shorten thetotal lens length.

Conditional Expression (6) defines the focus sensitivity ESB of thesecond focus lens unit LB.

If a value of |ESB| exceeds an upper limit of Conditional Expression(6), an amount of change in field curvature caused by focusing becomeslarge, which is undesirable.

If a value of |ESB| falls below a lower limit of Conditional Expression(6), an amount of movement of the second focus lens unit LB in focusingincreases. As a result, it becomes difficult to sufficiently shorten thetotal lens length.

Conditional Expression (7) defines a relationship between movingdistances of the first focus lens unit LA and the second focus lens unitLB, and the focal length of the entire system. By satisfying ConditionalExpression (7), it is possible to further shorten the total lens length.

If a value of (|MA|+|MB|)/f exceeds an upper limit of ConditionalExpression (7), it is advantageous for the suppression of an amount ofchange in spherical aberration and/or of field curvature in focusingbecomes, but an amount of movement in focusing increases. For thisreason, it becomes difficult to sufficiently shorten the total lenslength.

If a value of (|MA|+|MB|)/f falls below a lower limit of ConditionalExpression (7), it becomes difficult to ensure an amount of movement ofa focus lens unit required for changing an imaging magnification infocusing, while achieving a sufficiently-compact optical system.

Conditional Expression (8) defines a relationship between a distancefrom the aperture stop SP to the image plane, and the focal length ofthe entire system. By satisfying Conditional Expression (8), it ispossible to reduce a diameter of a lens disposed on the image side ofthe aperture stop SP, while increasing an imaging magnification.

If a value of Di/f exceeds an upper limit of Conditional Expression (8),because an amount of movement of a focus lens unit disposed on the imageside of the aperture stop SP becomes large, the optical system upsizes.

If a value of Di/f falls below a lower limit of Conditional Expression(8), an amount of movement of a focus lens unit disposed on the objectside of the aperture stop SP becomes too small, and an amount of changein spherical aberration and/or field curvature in focusing increases.

Conditional Expression (9) defines a relationship between a focal lengthof the lens unit L1 and a focal length of the entire system in anin-focus state on an infinite-distance object. By satisfying ConditionalExpression (9), it is possible to achieve both the further shortening ofthe total lens length and the suppression of spherical aberration.

If a value of fL1/f exceeds an upper limit of Conditional Expression(9), it is advantageous for the suppression of generation of sphericalaberration and/or comatic aberration, but the total lens length is proneto increase.

If a value of fL1/f falls below a lower limit of Conditional Expression(9), refractive power of the first lens unit L1 becomes too high, and acomatic aberration sensitivity of the first lens unit L1, when the firstlens unit L1 is decentered, becomes higher. Thus, excessive accuracy isrequired in the manufacturing of an optical system, which isundesirable.

Conditional Expression (10) defines a relationship between a focallength of the entire system and a focal length of a lens disposed at aposition closest to the image plane, in an in-focus state on aninfinite-distance object. By satisfying Conditional Expression (10), itis possible to reduce a lens diameter of the partial optical system LC.

If a value of fI/f exceeds an upper limit of Conditional Expression(10), it becomes difficult to shorten a back focus. As a result, itbecomes difficult to obtain a sufficiently-compact optical system.

If a value of fI/f falls below a lower limit of Conditional Expression(10), refractive power of a lens disposed closest to the image sidebecomes too high, and it becomes easier to generate distortionaberration and/or magnification chromatic aberration. As a result, itbecomes difficult to reduce a lens diameter of the partial opticalsystem LC when optical performance is to be maintained.

Conditional Expression (11) defines a maximum imaging magnification ineach of the exemplary embodiments.

If a value of βm exceeds an upper limit of Conditional Expression (11),a lateral magnification when an imaging magnification becomes maximumbecomes insufficient. As a result, it becomes difficult to perform imagecapturing while sufficiently enlarging a subject, which is undesirable.

If a value of βm falls below a lower limit of Conditional Expression(11), an absolute value of a lateral magnification when an imagingmagnification becomes maximum becomes too large. As a result, it becomesdifficult to sufficiently shorten the total lens length whilemaintaining optical performance, which is undesirable.

In addition, it is more desirable to set numerical value ranges ofConditional Expressions (2) to (11) to ranges of the followingConditional Expressions (2a) to (11a).

−1.10<fLCY/f<−0.25   (2a)

0.15<|fLAK|<0.45   (3a)

−0.95 <sk/fLCY<−0.15   (4a)

2.70<|ESA|<7.30   (5a)

2.30<|ESB|<5.70   (6a)

0.10<(|MA|+|MB|)<0.50   (7a)

0.60<Di/f<1.35   (8a)

0.20<fL1/f<2.20   (9a)

0.30<fI/f<2.00   (10a)

−4.00<βm<−1.23   (11a)

In addition, it is further desirable to set numerical value ranges ofConditional Expressions (2) to (11) to ranges of the followingConditional Expressions (2b) to (11b).

−1.05<fLCY/f<−0.28   (2b)

0.17<|fLA/f|<0.40   (3b)

−0.90<sk/fLCY<−0.20   (4b)

2.80<|ESA|<7.20   (5b)

2.40<|ESB|<5.60   (6b)

0.15<(|MA|+|MB|)/f<0.47   (7b)

0.63<Di/f<1.30   (8b)

0.30<fL1/f<2.10   (9b)

0.35<fI/f<1.90   (10b)

−3.50<βm<−1.26   (11b)

Next, a desirable configuration of the optical system according to eachof the exemplary embodiments will be described.

In the optical system according to each of the exemplary embodiments, alens disposed at a position closest to the image plane IP desirably haspositive refractive power. When a lens disposed at a position closest tothe image plane IP is a cemented lens, a lens disposed closest to theimage side among the cemented lens desirably has positive refractivepower in air. In a lens having a large imaging magnification such as amacro lens, a change in height of an off-axis light ray caused byfocusing from an infinite-distance object to a close-distance object islikely to be larger than that of a normal lens. By disposing a positivelens at a position closest to the image side, it is possible to preventan exit pupil from coming excessively on the image plane IP. With thisconfiguration, it becomes possible to suppress a variation inmagnification chromatic aberration and/or distortion aberration causedby focusing.

In addition, when more focus lens units are provided, it is possible tofurther reduce a variation in optical performance caused by focusing,but control of the lenses becomes complicated. In addition, a mechanismfor moving the focus lens units becomes complicated, and the opticalsystem may become large. For this reason, it is desirable that thenumber of focus lens units moving in focusing is to be three or less ineach of the exemplary embodiments. In other words, it is desirable thatthe number of focus lens units is two or three.

In addition, in order to further shorten the total lens length, thefirst lens unit L1 desirably has positive refractive power. In addition,when the first lens unit L1 has positive refractive power, the firstfocus lens unit LA desirably has negative refractive power. With thisconfiguration, it becomes possible to appropriately correct varioustypes of aberration generated in the first lens unit L1.

In addition, in the optical system according to each of the exemplaryembodiments, it is desirable that the first focus lens unit LA and thesecond focus lens unit LB are disposed on opposite sides with respect tothe aperture stop SP. More specifically, it is desirable that the firstfocus lens unit LA is disposed on a light incident side of the aperturestop SP, and the second focus lens unit LB is disposed on a lightemission side of the aperture stop SP. On the light incident side of theaperture stop SP, the height of an on-axis light ray is relatively high,and on the light emission side of the aperture stop SP, the height of anoff-axis light ray is relatively high. For this reason, by disposing thefirst focus lens unit LA and the second focus lens unit LB on oppositesides with respect to the aperture stop SP, it becomes possible toeffectively reduce an amount of change in optical performance caused byfocusing, over a wide range of a screen.

In addition, the first focus lens unit LA desirably includes three ormore lenses including a negative lens and a positive lens. In addition,the second focus lens unit LB desirably includes two or more lensesincluding a negative lens and a positive lens. This is because, by afocus lens unit including a negative lens and a positive lens, it ispossible to suppress the generation of on-axis chromatic aberrationand/or magnification chromatic aberration in focusing.

In addition, the first lens unit L1 is desirably immovable in focusing.With this configuration, it is possible to reduce a shift in gravitycenter of the optical system in focusing, and enhance operability infocusing.

Next, the optical system according to each of the exemplary embodimentswill be described in detail.

The optical system according to the first exemplary embodiment includes,in order from the object side to the image side, the first lens unit L1having positive refractive power, a second lens unit L2 having negativerefractive power, a third lens unit L3 including the aperture stop SPand having positive refractive power, a fourth lens unit L4 havingpositive refractive power, and a fifth lens unit L5 having negativerefractive power. The second lens unit L2 corresponds to the first focuslens unit LA, and moves toward the image side in focusing from aninfinite-distance object to a close-distance object. The fourth lensunit L4 corresponds to the second focus lens unit LB, and moves towardthe object side in focusing from an infinite-distance object to aclose-distance object. The fifth lens unit L5 corresponds to the partialoptical system LC. The lateral magnification Pm of the optical systemaccording to the first exemplary embodiment is −2.0.

The optical system according to the second exemplary embodimentincludes, in order from the object side to the image side, the firstlens unit L1 having positive refractive power, the second lens unit L2having negative refractive power, the aperture stop SP, the third lensunit L3 having positive refractive power, the fourth lens unit L4 havingpositive refractive power, and the fifth lens unit L5 having negativerefractive power. The second lens unit L2 corresponds to the first focuslens unit LA, and moves toward the image side in focusing from aninfinite-distance object to a close-distance object. The fourth lensunit L4 corresponds to the second focus lens unit LB, and moves towardthe object side in focusing from an infinite-distance object to aclose-distance object. The fifth lens unit L5 corresponds to the partialoptical system LC. In addition, the third lens unit L3 moves toward theobject side in focusing from an infinite-distance object to aclose-distance object. The lateral magnification βm of the opticalsystem according to the second exemplary embodiment is −2.0.

The optical system according to the third exemplary embodiment includes,in order from the object side to the image side, the first lens unit L1having positive refractive power, the second lens unit L2 havingnegative refractive power, the aperture stop SP, the third lens unit L3having positive refractive power, the fourth lens unit L4 havingnegative refractive power, and the fifth lens unit L5 having positiverefractive power. The second lens unit L2 corresponds to the first focuslens unit LA, and moves toward the image side in focusing from aninfinite-distance object to a close-distance object. The third lens unitL3 corresponds to the second focus lens unit LB, and moves toward theobject side in focusing from an infinite-distance object to aclose-distance object. A partial optical system including the fourthlens unit L4 and the fifth lens unit L5 has negative refractive power,and corresponds to the partial optical system LC. In addition, thefourth lens unit L4 moves toward the object side in focusing from aninfinite-distance object to a close-distance object. The lateralmagnification Pm of the optical system according to the third exemplaryembodiment is −1.5.

The optical system according to the fourth exemplary embodimentincludes, in order from the object side to the image side, the firstlens unit L1 having positive refractive power, the second lens unit L2having negative refractive power, the third lens unit L3 including theaperture stop SP and having positive refractive power, the fourth lensunit L4 having positive refractive power, the fifth lens unit L5 havingnegative refractive power, a sixth lens unit L6 having negativerefractive power, a seventh lens unit L7 having negative refractivepower, and an eighth lens unit L8 having negative refractive power. Thesecond lens unit L2 corresponds to the first focus lens unit LA, andmoves toward the image side in focusing from an infinite-distance objectto a close-distance object. The fourth lens unit L4 corresponds to thesecond focus lens unit LB, and moves toward the object side in focusingfrom an infinite-distance object to a close-distance object. The fifthto eighth lens units L5 to L8 have negative refractive power as a whole,and correspond to the partial optical system LC. In addition, the fifthlens unit L5 moves toward the object side in focusing from aninfinite-distance object to a close-distance object, and the seventhlens unit L7 moves toward the image side in focusing from aninfinite-distance object to a close-distance object. The lateralmagnification βm of the optical system according to the fourth exemplaryembodiment is −2.8.

The optical system according to the fifth exemplary embodiment includes,in order from the object side to the image side, the first lens unit L1having positive refractive power, the second lens unit L2 havingnegative refractive power, the third lens unit L3 including the aperturestop SP and having positive refractive power, the fourth lens unit L4having negative refractive power, and the fifth lens unit L5 havingnegative refractive power. The second lens unit L2 corresponds to thefirst focus lens unit LA, and moves toward the image side in focusingfrom an infinite-distance object to a close-distance object. The fourthlens unit L4 corresponds to the second focus lens unit LB, and movestoward the image side in focusing from an infinite-distance object to aclose-distance object. The fifth lens unit L5 corresponds to the partialoptical system LC. The lateral magnification βm of the optical systemaccording to the fifth exemplary embodiment is −1.5.

The optical system according to the sixth exemplary embodiment includes,in order from the object side to the image side, the first lens unit L1having positive refractive power, the second lens unit L2 havingnegative refractive power, the third lens unit L3 including the aperturestop SP and having positive refractive power, the fourth lens unit L4having negative refractive power, and the fifth lens unit L5 havingnegative refractive power. The second lens unit L2 corresponds to thefirst focus lens unit LA, and moves toward the image side in focusingfrom an infinite-distance object to a close-distance object. The fourthlens unit L4 corresponds to the second focus lens unit LB, and movestoward the image side in focusing from an infinite-distance object to aclose-distance object. The fifth lens unit L5 corresponds to the partialoptical system LC. In addition, the fifth lens unit L5 moves toward theimage side in focusing from an infinite-distance object to aclose-distance object. The lateral magnification βm of the opticalsystem according to the sixth exemplary embodiment is −2.0.

The optical system according to the seventh exemplary embodimentincludes, in order from the object side to the image side, the firstlens unit L1 having negative refractive power, the second lens unit L2having positive refractive power, the third lens unit L3 including theaperture stop SP and having negative refractive power, the fourth lensunit L4 having positive refractive power, and the fifth lens unit L5having negative refractive power. The second lens unit L2 corresponds tothe first focus lens unit LA, and moves toward the object side infocusing from an infinite-distance object to a close-distance object.The fourth lens unit L4 corresponds to the second focus lens unit LB,and moves toward the object side in focusing from an infinite-distanceobject to a close-distance object. The fifth lens unit L5 corresponds tothe partial optical system LC. The lateral magnification βm of theoptical system according to the seventh exemplary embodiment is −1.3.

The optical system according to the eighth exemplary embodimentincludes, in order from the object side to the image side, the firstlens unit L1 having positive refractive power, the second lens unit L2having positive refractive power, the third lens unit L3 including theaperture stop SP and having negative refractive power, the fourth lensunit L4 having negative refractive power, and the fifth lens unit L5having negative refractive power. The second lens unit L2 corresponds tothe first focus lens unit LA, and moves toward the object side infocusing from an infinite-distance object to a close-distance object.The fourth lens unit L4 corresponds to the second focus lens unit LB,and moves toward the image side in focusing from an infinite-distanceobject to a close-distance object. The fifth lens unit L5 corresponds tothe partial optical system LC. The lateral magnification βm of theoptical system according to the eighth exemplary embodiment is −1.5.

Numerical Examples 1 to 8 respectively corresponding to the first toeighth exemplary embodiments will be described below.

In surface data of each numerical example, “r” denotes a curvatureradius of each optical surface, and “d” (mm) denotes an on-axis interval(distance on an optical axis) between an m-th surface and an (m+1)-thsurface. Here, “m” denotes an ordinal number of a surface counted fromthe light incident side. In addition, “nd” denotes refractive index withrespect to d-line of each optical component, and “vd” denotes Abbenumber of each optical component.

In addition, in each numerical example, all values of “d”, focal length(mm), F-number, and half field angle (°) are values obtained when theoptical system according to each of the exemplary embodiments isin-focus state on an infinite-distance object. A back focus BF is adistance from a final lens surface to the image plane. The total lenslength is a value obtained by adding a back focus to a distance from afirst lens surface to a final lens surface.

In addition, in each numerical example, an aspherical-shaped lenssurface is indicated by asterisk (*) added after a surface number. Inaddition, “e±P” in aspherical surface data means “×10 ^(±P)”. Anaspherical surface shape of an optical surface is represented by thefollowing Expression A:

x=(h ² /R)/[1+{1−(1+k)(h/R)²}^(1/2)]+A4×h ⁴ +A6×h ⁶ +A8×h ⁸   A,

where x is an amount of displacement from a surface vertex in an opticalaxis direction, h is a height from an optical axis in a directionvertical to the optical axis direction, R is a paraxial curvatureradius, K is a conic constant, and A4, A6, and A8 are aspherical surfacecoefficients.

[Numerical Example 1]

Unit: mm Surface data Surface number r d nd νd  1 115.041 4.96 2.0006925.5  2 −298.226 1.20 1.53172 48.8  3 40.529 3.20  4 76.747 6.59 1.5952267.7  5 −118.732 0.15  6 130.015 7.45 1.60311 60.6  7 −46.212 1.202.00069 25.5  8 −374.729 0.20  9 39.827 6.48 1.49700 81.5 10 −98.026(variable) 11 −142.559 1.20 1.83481 42.7 12 33.718 3.80 13 −73.427 1.201.74320 49.3 14 33.507 4.63 1.80810 22.8 15 ∞ (variable) 16 ∞ 0.20 17(stop) ∞ 1.11 18 328.213 3.59 1.61997 63.9 19 −59.848 (variable) 2069.543 4.29 1.59522 67.7 21 −76.731 0.20 22 61.230 5.38 1.60300 65.4 23−38.999 2.00 1.76182 26.5 24 −310.133 (variable) 25 633.353 1.20 1.8010035.0 26 27.848 2.84 27 35.158 1.38 1.48749 70.2 28 40.315 2.85 1.4874970.2 29 165.151 6.60 30 −103.219 4.57 1.80810 22.8 31 −24.960 1.201.48749 70.2 32 44.976 8.95 33 −21.059 1.20 1.61800 63.3 34 −56.682 0.2035 58.438 4.39 1.60311 60.6 36 −447.212 23.38  37 ∞ 1.50 1.51633 64.1 38∞ 0.37 Image plane ∞ Various kinds of data Focal length 99.70 F-number2.92 Half field angle (°) 12.24 Image height 21.64 Total lens length164.46 BF 24.74 Magnification ∞ −1.0 −1.2 −2.0 d10 1.00 11.11 13.3521.24 d15 21.24 11.13 8.90 1.00 d19 22.07 10.70 8.33 1.00 d24 1.00 12.3614.74 22.07 Lens unit data Unit Start surface Focal length 1 1 41.49 211 −25.11 3 16 81.94 4 20 41.27 5 25 −31.63

[Numerical Example 2]

Unit: mm Surface data Surface number r d nd νd  1 85.290 5.22 1.9165031.6  2 −257.004 2.93 1.57135 53.0  3 38.839 1.99  4 57.219 6.93 1.4387594.9  5 −99.117 0.10  6 90.064 6.53 1.53775 74.7  7 −49.382 0.97 2.0010029.1  8 −279.109 0.10  9 36.255 6.06 1.43875 94.9 10 −103.644 (variable)11 −201.431 0.95 1.81600 46.6 12 30.483 4.64 13 −93.270 0.97 1.5928268.6 14 32.887 4.07 1.78472 25.7 15 227.240 (variable) 16 ∞ 0.47 17(stop) ∞ (variable) 18 686.622 4.34 1.53775 74.7 19 −53.732 (variable)20 62.211 4.29 1.43875 94.9 21 −76.198 0.07 22 93.757 4.03 1.53775 74.723 −45.927 1.82 1.75520 27.5 24 −153.709 (variable) 25 311.541 4.401.80610 33.3 26 32.686 1.36 27 35.676 2.98 1.64000 60.1 28 43.556 5.001.95906 17.5 29 50.034 4.71 30 −1008.598 5.03 1.64769 33.8 31 −22.6132.00 1.51633 64.1 32 57.920 9.80 33 −20.232 1.68 1.53775 74.7 34−105.272 0.20 35 68.348 5.72 1.75500 52.3 36 −260.009 22.00  37 ∞ 1.501.51633 64.1 38 ∞ 0.36 Image plane ∞ Various kinds of data Focal length111.55 F-number 2.92 Half field angle (°) 10.98 Image height 21.64 Totallens length 170.07 BF 23.35 Magnification ∞ −1.0 −1.2 −2.0 d10 0.10 9.2011.25 17.74 d15 18.64 9.53 7.49 1.00 d17 10.24 6.88 5.71 1.00 d19 17.275.91 4.44 0.10 d24 1.12 15.83 18.48 27.53 Lens unit data Unit Startsurface Focal length 1 1 42.28 2 11 −28.07 3 18 92.86 4 20 54.36 5 25−35.12

[Numerical Example 3]

Unit: mm Surface data Surface number r d nd νd  1 114.017 4.02 1.8348142.7  2 −129.357 1.22  3 41.490 4.73 1.43875 94.9  4 −152.883 0.63  5−91.942 0.70 1.96300 24.1  6 120.327 0.19  7 33.297 4.00 1.43875 94.9  8−220.670 (variable)  9 −1358.413 0.98 1.75500 52.3 10 23.285 3.61 11−227.223 0.99 1.63930 44.9 12 23.180 3.58 1.85896 22.7 13 106.679(variable) 14 ∞ 0.48 15 (stop) ∞ (variable) 16 75.913 5.01 1.49700 81.517 −49.042 0.04 18 44.446 6.98 1.49700 81.5 19 −38.982 1.60 1.62004 36.320 −169.950 (variable) 21 111.697 2.72 1.75500 52.3 22 23.318 (variable)23 32.386 6.14 2.00100 29.1 24 125.586 1.30 1.80810 22.8 25 34.640 7.3226 −25.350 1.20 1.59282 68.6 27 −266.543 0.51 28 51.360 8.18 1.4970081.5 29 −75.306 25.12  30 ∞ 1.50 1.51633 64.1 31 ∞ 0.37 Image plane ∞Various kinds of data Focal length 87.55 F-number 2.92 Half field angle(°) 13.88 Image height 21.64 Total lens length 142.88 BF 26.49Magnification ∞ −1.0 −1.2 −1.5 d8 0.26 10.40 11.57 12.92 d13 13.83 3.702.52 1.18 d15 25.22 8.68 5.57 0.99 d20 7.91 20.96 24.57 29.95 d22 3.036.51 6.02 5.22 Lens unit data Unit Start surface Focal length 1 1 42.792 9 −28.65 3 16 36.08 4 21 −39.56 5 23 195.21

[Numerical Example 4]

Unit: mm Surface data Surface number r d nd νd  1 74.790 5.74 1.9108235.3  2 −307.571 1.62 1.53775 74.7  3 38.330 1.90  4 53.851 7.31 1.4387594.9  5 −93.659 0.07  6 59.550 7.10 1.43875 94.9  7 −44.235 0.95 2.0006925.5  8 −164.661 0.10  9 43.409 4.59 1.49700 81.5 10 −86.408 (variable)11 −122.734 0.97 1.85150 40.8 12 26.875 3.96 13 −59.975 0.92 1.6968055.5 14 28.933 3.57 1.85896 22.7 15 229.535 (variable) 16 ∞ 0.37 17(stop) ∞ 0.88 18 5369.938 3.54 1.59282 68.6 19 −56.682 (variable) 2087.558 4.96 1.43875 94.9 21 −53.346 −0.05  22 40.433 6.61 1.43875 94.923 −47.075 1.19 1.73800 32.3 24 −111.190 (variable) 25 28.369 1.811.75700 47.8 26 20.367 (variable) 27 33.781 4.65 1.67270 32.1 28−887.252 2.88 2.00069 25.5 29 40.642 (variable) 30 −48.362 6.01 2.0006925.5 31 −34.690 2.50 1.51823 58.9 32 −172.798 (variable) 33 −38.708 1.331.72916 54.7 34 73.913 0.18 35 46.440 5.51 1.85478 24.8 36 320.70025.00  37 ∞ 1.50 1.51633 64.1 38 ∞ 0.38 Image plane ∞ Various kinds ofdata Focal length 97.07 F-number 2.92 Half field angle (°) 12.56 Imageheight 21.64 Total lens length 177.88 BF 26.37 Magnification ∞ −1.0 −1.2−2.8 d10 0.12 8.75 10.64 19.95 d15 20.83 12.19 10.31 1.00 d19 33.8819.61 16.97 1.00 d24 0.22 9.03 10.81 24.21 d26 2.87 8.33 9.19 11.77 d293.91 8.34 8.79 8.30 d32 8.50 4.07 3.62 4.11 Lens unit data Unit Startsurface Focal length 1 1 37.25 2 11 −19.88 3 16 94.64 4 20 41.79 5 25−105.69 6 27 −333.13 7 30 −369.69 8 33 −77.66

[Numerical Example 5]

Unit: mm Surface data Surface number r d nd νd  1 237.159 3.97 1.5952267.7  2 −138.265 0.14  3 70.172 4.92 1.59522 67.7  4 −213.463 1.27  5−136.032 1.19 1.80810 22.8  6 184.319 0.19  7 31.946 4.06 1.80810 22.8 8 26.285 1.23  9 33.957 4.15 1.59522 67.7 10 2307.010 (variable) 11−309.389 0.99 1.88300 40.8 12 31.039 5.19 13 −63.445 0.84 1.76385 48.514 42.029 3.79 1.80810 22.8 15 −93.464 (variable) 16 (stop) ∞ 3.00 17925.313 5.66 1.48749 70.2 18 −36.874 3.01 19 42.040 5.55 1.65160 58.5 20−70.827 1.10 1.96300 24.1 21 −144.265 (variable) 22 −42.225 1.13 1.7340051.5 23 61.187 7.78 24 1917.613 4.80 1.76385 48.5 25 −36.897 (variable)26 −50.032 4.00 2.00069 25.5 27 124.454 0.02 28 110.649 4.55 1.4874970.2 29 −254.409 21.52  30 ∞ 1.50 1.51633 64.1 31 ∞ 0.50 Image plane ∞Various kinds of data Focal length 87.51 F-number 2.92 Half field angle(°) 13.89 Image height 21.64 Total lens length 156.89 BF 23.01Magnification ∞ −1.0 −1.2 −1.5 d10 0.94 21.82 25.73 30.69 d15 31.4010.51 6.60 1.64 d21 1.74 18.16 21.53 28.05 d25 27.29 10.87 7.49 0.97Lens unit data Unit Start surface Focal length 1 1 50.01 2 11 −30.25 316 32.88 4 22 −589.89 5 26 −46.20

[Numerical Example 6]

Unit: mm Surface data Surface number r d nd νd  1 500.000 3.41 1.5928268.6  2 −157.319 0.10  3 50.189 5.30 1.72916 54.7  4* −986.012 1.29  5−219.904 1.06 1.92286 20.9  6 228.546 0.03  7 117.713 1.36 2.00069 25.5 8 49.166 −0.07   9 41.015 6.89 1.59522 67.7 10 −83.063 (variable) 111295.851 0.94 1.81600 46.6 12 29.227 5.23 13 −55.392 0.63 1.69350 50.814 29.582 4.14 1.92286 20.9 15 539.950 (variable) 16 (stop) ∞ 1.79 17106.286 5.53 1.59522 67.7 18* −43.684 3.02 19 62.655 6.12 1.59522 67.720 −30.037 0.94 2.00069 25.5 21 −54.423 (variable) 22 −42.852 1.081.59282 68.6 23 40.106 20.65  24 −181.857 4.82 1.69930 51.1 25 −34.638(variable) 26 −66.535 1.19 2.00069 25.5 27 94.110 1.29 28 94.110 3.221.48749 70.2 29 −300.000 12.27  30 ∞ 1.50 1.51633 64.1 31 ∞ 0.44 Imageplane ∞ Aspherical surface data Fourth surface K = 0.00000e+000 A4 =2.58513e−006 A6 = −4.47243e−010 A8 = 1.68012e−012 Eighteenth surface K =0.00000e+000 A4 = 9.95902e−007 A6 =−3.39682e−011 A8 = −1.43118e−012Various kinds of data Focal length 87.58 F-number 2.92 Half field angle(°) 13.88 Image height 21.64 Total lens length 161.43 BF 13.70Magnification ∞ −1.0 −1.2 −2.0 d10 0.61 15.16 18.12 27.53 d15 28.3613.81 10.84 1.43 d21 0.97 17.91 21.81 38.44 d25 37.8 20.91 17.01 0.98Lens unit data Unit Start surface Focal length 1 1 47.55 2 11 −28.82 316 31.66 4 22 −1815.99 5 26 −53.75

[Numerical Example 7]

Unit: mm Surface data Surface number r d nd νd  1 50.145 5.00 1.4387594.9  2 −681.596 2.00 1.65412 39.7  3 60.273 (variable)  4 41.198 5.901.88300 40.8  5 −591.996 0.11  6* 48.387 1.11 1.96300 24.1  7 24.6447.20 1.59522 67.7  8 −440.997 (variable)  9 −262.028 1.11 1.65160 58.510 16.355 4.56 1.80810 22.8 11 27.780 3.29 12 ∞ 0.36 13 (stop) ∞ 0.79 14−406.850 0.80 1.61800 63.3 15 46.406 (variable) 16* 105.635 1.38 1.8589622.7 17 24.111 8.22 1.89190 37.1 18 −39.767 (variable) 19 103.411 1.181.96300 24.1 20 32.474 14.43  21 −25.796 4.50 1.91650 31.6 22 −78.4070.19 23 −323.723 8.89 1.72825 28.5 24 −29.595 29.07  25 ∞ 1.50 1.5163364.1 26 ∞ 0.30 Image plane ∞ Aspherical surface data Sixth surface K =0.00000e+000 A4 = −2.44854e−006 A6 = −1.45860e−009 A8 = −3.67049e−012Sixteenth surface K = 0.00000e+000 A4 = −8.81694e−006 A6 = −2.05356e−009A8 = −7.47750e−012 Various kinds of data Focal length 100.00 F-number2.92 Half field angle (°) 12.21 Image height 21.64 Total lens length133.45 BF 30.36 Magnification ∞ −1.0 −1.2 −1.3 d3 14.84 2.70 0.99 0.18d8 0.82 12.96 14.66 15.48 d15 14.96 9.21 6.56 5.27 d18 1.46 7.21 9.8711.15 Lens unit data Group Start surface Focal length 1 1 −508.03 2 434.65 3 9 −26.54 4 16 32.41 5 19 −100.11

[Numerical Example 8]

Unit: mm Surface data Surface number r d nd νd  1 309.543 6.87 1.6034238.0  2 −56.853 1.50 1.91082 35.3  3 −337.400 0.20  4 706.618 4.041.59282 68.6  5 −103.752 0.19  6 36.947 3.80 1.78472 25.7  7 61.026 4.20 8 45.266 1.29 2.00069 25.5  9 28.449 (variable) 10 31.551 1.19 2.0006925.5 11 23.542 5.24 1.59522 67.7 12 122.935 0.29 13 39.982 3.78 1.5952267.7 14 −576.650 (variable) 15 (stop) ∞ 2.03 16 −46.435 1.20 1.8044039.6 17 30.267 3.88 18 −2325.853 3.71 1.74077 27.8 19 −32.818 2.991.48749 70.2 20 −26.802 (variable) 21 −80.286 4.50 1.91082 35.3 22−17.723 1.07 1.60342 38.0 23 76.812 (variable) 24 −20.525 1.19 1.9108235.3 25 −75.757 1.44 1.85896 22.7 26 −66.498 1.18 27* 37.095 4.001.80810 22.8 28 55.754 4.51 1.51633 64.1 29 −314.637 22.22  30 ∞ 1.501.51633 64.1 31 ∞ 0.47 Image plane ∞ Aspherical surface dataTwenty−seventh surface K = 0.00000e+000 A4 = −7.61233e−006 A6 =7.25390e−009 A8 = −5.55141e−012 Various kinds of data Focal length118.66 F-number 2.92 Half field angle (°) 10.33 Image height 21.64 Totallens length 137.11 BF 23.67 Magnification ∞ −1.0 −1.2 −1.5 d9 24.22 8.795.95 1.83 d14 0.47 15.90 18.73 22.86 d20 7.28 12.66 15.00 19.81 d2317.18 11.79 9.46 4.64 Lens unit data Group Start surface Focal length 11 237.94 2 10 39.94 3 15 −98.01 4 21 −637.80 5 24 −100.04

Various values in each numerical example are listed in Table 1 providedbelow.

TABLE 1 N.E. N.E. N.E. N.E. N.E. N.E. N.E. N.E. 1 2 3 4 5 6 7 8Conditional fLCX/fX −0.70 −0.78 0.68 −0.70 −1.01 −1.24 −1.47 −2.19Expression (1) Conditional fLCY/f −0.32 −0.31 −0.37 −0.32 −0.53 −0.61−1.00 −0.84 Expression (2) Conditional |fLA/f| 0.25 0.25 0.33 0.20 0.350.33 0.35 0.34 Expression (3) Conditional sk/fLCY −0.78 −0.64 −0.82−0.84 −0.50 −0.25 −0.30 −0.24 Expression (4) Conditional |ESA| 5.48 6.834.09 6.11 2.85 3.12 6.29 7.04 Expression (5) Conditional |ESB| 5.57 4.243.80 4.98 2.46 3.59 4.24 3.98 Expression (6) Conditional (|MA| + 0.220.21 0.30 0.24 0.43 0.36 0.18 0.18 Expression (7) |MB|)/f ConditionalDi/f 1.01 0.97 1.19 1.22 1.06 1.17 0.88 0.68 Expression (8) ConditionalfL1/f 0.42 0.38 0.49 0.38 0.57 0.54 — 2.01 Expression (9) ConditionalfI/f 0.86 0.65 0.72 0.65 1.82 1.68 0.44 0.78 Expression (10) Conditionalβm −2.00 −2.00 −1.50 −2.80 −1.50 −2.00 −1.30 −1.50 Expression (11) N.E.= Numerical Example

Imaging Apparatus

Next, a digital still camera (imaging apparatus) that uses an opticalsystem according to one of the exemplary embodiments of the presentinvention as an imaging optical system will be described with referenceto FIG. 17 . In FIG. 17 , the digital still camera includes a cameramain body 10, and an imaging optical system 11 including any of theoptical systems described in the first to eighth exemplary embodiments.The digital still camera further includes a solid-state image sensor(photoelectric conversion element) 12 such as a CCD sensor or a CMOSsensor that is built in the camera main body 10, and that receives andphotoelectrically converts an optical image formed by the imagingoptical system 11. The camera main body 10 may be a so-calledsingle-lens reflex camera including a quick return mirror, or may be aso-called mirrorless camera not including an instant return mirror.

In this manner, by using the optical system according to an exemplaryembodiment of the present invention for an imaging apparatus such as adigital still camera, it is possible to perform image capturing at animaging magnification of a same magnification or more, and it ispossible to obtain a compact imaging apparatus having high opticalperformance.

Hereinbefore, the exemplary embodiments of the present invention havebeen described, but the present invention is not limited to theseexemplary embodiments, and various combinations, modifications, andchanges can be made within the scope of the present invention.

According to an exemplary embodiment of the present invention, it ispossible to realize a compact optical system that has high opticalperformance and can perform image capturing at an imaging magnificationof a same magnification or more.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. An optical system in which an interval betweenadjacent lens units is configured to change during focusing from aninfinite-distance object to a close-distance object, and in which in afirst in-focus state β=−1.2 is satisfied, where β is a lateralmagnification of the optical system, the optical system comprising: aplurality of focus lens units configured to move during focusing from aninfinite-distance object to a close-distance object, wherein theplurality of focus lens units includes a first focus lens unit (LA) anda second focus lens unit (LB) disposed on an image side of the firstfocus lens unit (LA), the first focus lens unit (LA) being one of afocus lens unit having a largest absolute value of a focus sensitivityor a focus lens unit having a second largest absolute value of a focussensitivity among the plurality of focus lens units in an in-focus stateon an infinite-distance object, the second focus lens unit (LB) beingthe other lens unit having the largest absolute value of a focussensitivity or the focus lens unit having the second largest absolutevalue of a focus sensitivity among the plurality of focus lens unit inthe in-focus state on the infinite-distance object, wherein a partialoptical system (LC) including all lenses disposed on the image side ofthe second focus lens unit (LB) has negative refractive power.
 2. Theoptical system according to claim 1, wherein the following conditionalexpression is satisfied:0.10<|fLA/f|<0.50, where fLA is a focal length of the first focus lensunit (LA) and f is a focal length of the optical system in an in-focusstate on an infinite-distance object.
 3. The optical system according toclaim 1, wherein the following conditional expression is satisfied:−1.00<sk/fLCY<−0.10, where sk is a distance from an image-side lenssurface of a lens disposed closest to the image side in the opticalsystem to an image plane (IP) in an in-focus state on aninfinite-distance object and fLCY is a focal length of the partialoptical system (LC) in a second in-focus state in which β=−1.0 issatisfied.
 4. The optical system according to claim 1, wherein thefollowing conditional expression is satisfied:0.10<|ESB|<6.00, where ESB is a focus sensitivity of the second focuslens unit (LB) in an in-focus state on an infinite-distance object. 5.The optical system according to claim 1, wherein the followingconditional expression is satisfied:0.05<(|MA|+|MB|)/f<0.60, where f is a focal length of the optical systemin an in-focus state on an infinite-distance object , MA is an amount ofmovement of the first focus lens unit (LA) moved from an in-focus stateon an infinite-distance object to the second in-focus state, whereβ=−1.0, and MB is an amount of movement of the second focus lens unit(LB) moved from an in-focus state on an infinite-distance object to thesecond in-focus state.
 6. The optical system according to claim 1,further comprising an aperture stop, wherein the following conditionalexpression is satisfied:0.50<Di/f<1.50, where Di is a distance from the aperture stop to animage plane in an in-focus state on an infinite-distance object and f isa focal length of the optical system in an in-focus state on aninfinite-distance object.
 7. The optical system according to claim 1,wherein a first lens unit (L1) disposed closest to the object side inthe optical system has positive refractive power.
 8. The optical systemaccording to claim 7, wherein the following conditional expression issatisfied:0.10<fL1/f<2.50, where fL1 is a focal length of the first lens unit (L1)and f is a focal length of the optical system in an in-focus state on aninfinite-distance object.
 9. The optical system according to claim 7,wherein the first focus lens unit (LA) has negative refractive power.10. The optical system according to claim 1, wherein a lens disposedclosest to an image side in the optical system has positive refractivepower.
 11. The optical system according to claim 10, wherein thefollowing conditional expression is satisfied:0.25<fI/f<2.20, where fI is a focal length of the lens disposed closestto the image side in the optical system and f is a focal length of theoptical system in an in-focus state on an infinite-distance object. 12.The optical system according to claim 1, wherein the followingconditional expression is satisfied:−5.0<βm<−1.2, where βm is a lateral magnification when imagingmagnification is largest in the optical system.
 13. The optical systemaccording to claim 1, further comprising an aperture stop, wherein thefirst focus lens unit LA is disposed on a light incident side of theaperture stop, and wherein the second focus lens unit LB is disposed ona light emission side of the aperture stop.
 14. The optical systemaccording to claim 1, wherein the first focus lens unit (LA) includesthree or more lenses including a negative lens and a positive lens. 15.The optical system according to claim 1, wherein the second focus lensunit (LB) includes two or more lenses including a negative lens and apositive lens.
 16. The optical system according to claim 1, wherein afirst lens unit (L1) disposed closest to the object side in the opticalsystem is immovable during focusing.
 17. The optical system according toclaim 1, wherein the following conditional expression is satisfied:−3.00<fLCX/fX<−0.50, where fLCX is a focal length of the partial opticalsystem (LC) in the first in-focus state, and fX is a focal length of theoptical system in the first in-focus state.
 18. The optical systemaccording to claim 1, wherein the following conditional expression issatisfied:−1.20<fLCY/f<−0.20, where fLCY is a focal length of the partial opticalsystem (LC) in a second in-focus state in which β=−1.0 is satisfied, andf is a focal length of the optical system in an in-focus state on aninfinite-distance object,.
 19. The optical system according to claim 1,wherein the following conditional expression is satisfied:2.50<|ESA|<7.5, where ESA is a focus sensitivity of the first focus lensunit (LA) in an in-focus state on an infinite-distance object.
 20. Animaging apparatus comprising: an optical system; and an image sensorconfigured to photoelectrically convert an optical image formed by theoptical system, wherein, in the optical system, an interval betweenadjacent lens units changes in focusing from an infinite-distance objectto a close-distance object, and a first in-focus state in which β=−1.2is satisfied can be achieved, where β is a lateral magnification of anentire system, wherein the optical system includes a plurality of focuslens units configured to move in focusing from an infinite-distanceobject to a close-distance object, wherein the plurality of focus lensunits includes a first focus lens unit (LA) and a second focus lens unit(LB) disposed on an image side of the first focus lens unit (LA), thefirst focus lens unit (LA) being one out of a focus lens unit having alargest absolute value of a focus sensitivity or a focus lens unithaving a second largest absolute value of focus sensitivity among theplurality of focus lens units in an in-focus state on aninfinite-distance object, and the second focus lens unit (LB) being theother of the focus lens unit having the largest absolute value of afocus sensitivity or the focus lens unit having the second absolutevalue of a focus sensitivity among the plurality of focus lens units inthe in-focus state on the infinite-distance object, wherein a partialoptical system LC including all lenses disposed on the image side of thelens unit LB has negative refractive power.